The NM_005629.4:c.1141G>C variant in SLC6A8 is a missense variant that is predicted to lead to the substitution of a glycine for an arginine at amino acid 381 (p.Gly381Arg). This variant has been previously reported in one family with 5 affected males with elevated urinary creatine/creatinine and deficient creatine uptake in cultured fibroblasts (PP4_Strong) and segregated with disease in this family (PP1_Strong) (PMID: 11898126). This variant was reported to result in reduced (<10% of wild-type) creatine transport activity in SLC6A8 deficient fibroblasts (PMID: 22281021) (PS3_Supporting). In addition, the variant was shown to result in altered splicing via RT-PCR analysis (PMID: 11898126). The variant is absent in gnomAD v2.1.1. (PM2_Supporting). The computational predictor REVEL gives a score of 0.923 which is above the threshold of 0.75, evidence that correlates with impact to SLC6A8 function (PP3). There is a ClinVar entry for this variant (Variation ID 11697, zero-star review status), with one submitter classifying the variant as pathogenic. In summary, this variant meets criteria to be classified as pathogenic for creatine transporter deficiency. SLC6A8-specific criteria applied, as specified by the ClinGen CCDS VCEP (Specifications Version 1.1.0): PS3_Supporting, PM2_Supporting, PP3, PP1_Strong, PP4_Strong. (Classification approved by the ClinGen Cerebral Creatine Deficiency Syndromes Variant Curation Expert Panel on March 28, 2024).